1. Field of the Invention
The present invention relates to electromagnetic-shielding transparent window members useful as, for example, front filters for plasma display panels (PDPs) or window materials (for example, patch films) used in buildings requiring electromagnetic shielding, such as hospitals, and also relates to methods for producing the window members. In particular, the present invention relates to an electromagnetic-shielding transparent window member including a film and a patterned conductor formed thereon, and a method for producing the window member.
2. Description of the Related Art
In recent years, the widespread use of office automation (OA) equipment and communications equipment has developed the problem of electromagnetic waves generated from such equipment. For example, the electromagnetic waves may affect the human body and cause precision equipment to malfunction.
To cope with the problem, electromagnetic-shielding transparent window members have been developed as front filters for PDPs in OA equipment and have been put into practical use. Such window members are also used in sites with installed precision equipment, such as hospitals and laboratories, to protect the equipment from electromagnetic waves generated from, for example, cellular phones.
A conventional electromagnetic-shielding transparent window member mainly includes a conductive mesh, like a wire mesh, or transparent conductive film disposed between and integrated with transparent substrates, such as acrylic boards.
General conductive meshes for use in conventional electromagnetic-shielding transparent window members have a wire diameter of 10 to 500 μm, range from about 5 to 500 mesh, and have an aperture ratio below 75%.
In general, conductive meshes composed of thicker conductive fibers are coarser while conductive meshes composed of thinner conductive fibers are finer. A coarse mesh can be produced with thick fibers, but is extremely difficult to produce with thin fibers.
Accordingly, conventional electromagnetic-shielding transparent window members including such conductive meshes have a light transmittance of, at most, about 70%. The window members therefore cannot provide high light transmittance.
In addition, conventional conductive meshes readily cause a moiré pattern (interference fringes) in connection with pixel pitches of light-emitting panels equipped with the electromagnetic-shielding transparent window members.
The use of a transparent conductive film requires design changes such as the formation of through holes in a transparent substrate to bring the film into conduction. Such design changes complicate the assembly and incorporation of electromagnetic-shielding transparent window members into casings.